1. Field of the Invention
The present invention relates to a cooling apparatus for cooling a substrate such as a semiconductor wafer or a glass substrate, and a substrate treating apparatus in which the cooling apparatus is incorporated.
2. Description of the Related Art
In order to form a circuit on a surface of a substrate such as a semiconductor wafer or a glass substrate, exposure is performed to a resist film formed on the substrate surface so as to make a predetermined pattern. If the temperature of the substrate is high at the time of such exposure, expansion of the substrate will occur, which results in displacement of the focal length. Therefore, the substrate needs to be cooled to room temperature before the exposure.
For example, patent document 1 discloses that a resist liquid is supplied to a surface of a substrate by a spin coater, a resist film is formed by heating in a baking portion. A cooling plate in a treating unit is used as a place for delivering the substrate when the resist film is cooled by the cooling plate.
Patent document 2 discloses an apparatus which comprises a hot plate for a baking treatment after exposure, a cooling plate for a cooling treatment, and a special arm for delivering between the hot plate and the cooling plate. In this apparatus, if any trouble occurs in a subsequent process, the special arm transfers a substrate which has undergone a baking treatment for a predetermined period of time from the hot plate to the cooling plate so as to decrease the temperature of the substrate to a temperature which does not affect uniformity of the width.
Patent document 3 discloses that a cooling plate is provided in the course of a wafer transfer line, a central table movable in a vertical direction is provided around the center of the cooling plate, and a refrigerant is supplied into the cooling plate, so that heat exchange occurs between the refrigerant and the wafer mounted on the cooling plate.    Patent document 1: Japanese Patent Application publication No. 2004-207750    Patent document 2: Japanese Patent Application publication No. 2004-319626    Patent document 3: Japanese Patent Application publication No. 2006-294860
In a conventional cooling plate (cooling apparatus), a refrigerant passage is formed in an aluminum-alloy block by cutting as shown in FIG. 7. This makes it difficult to manufacture the apparatus, and also results in increase of its weight.
Further, since the distance between the cooling plate surface and the refrigerant varies depending on the place, the surface temperature of the cooling plate becomes non-uniform, which affects the accuracy of exposure. Furthermore, as the substrate becomes larger, the thickness of the aluminum-alloy block is increased, which requires more time to cool the substrate.